Wire Attracts Loop - Electromagnetic Unit

A rectangular loop of wire is placed next to a straight wire, as shown above. There is a current I in both the straight wire and the loop. The dimensions shown in the figure are a, b = 2.2a, and c = 8a. What is the magnitude of the force on the loop? Express your answer in terms of I, a, and μ0.

2. Relevant equations

B = (μ0 * I)/(2pi*d)

3. The attempt at a solution

Wouldn't I just use the equation from above and just use the value for b as the distance (d) ?

What is different in this problem that would require the equation to be different